Refractory element, assembly and tundish for transferring molten metal

ABSTRACT

A refractory element is configured to prevent or limit steel reoxidation in a steel casting process. The refractory element contains a base surrounded by a periphery in a specified geometrical arrangement. The refractory element is constituted of a base surrounded by a periphery in a specified geometrical arrangement.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to the continuous casting of steel andparticularly to the problem of steel reoxidation. In particular, theinvention relates to a tundish comprising an assembly comprising anozzle and a surrounding refractory element preventing or limiting steelreoxidation, and preventing oxidation products from entering a castingchannel. The invention also relates to an assembly comprising a nozzleand a surrounding refractory element preventing or limiting steelreoxidation, and preventing oxidation products from entering a castingchannel. According to other of its aspects, the invention also relatesto such a surrounding refractory element and to a continuous steelcasting process.

With growing demands for quality and property control, cleanliness ofsteel becomes more and more important. Issues like controlling thechemical composition and the homogeneity have been supplanted byconcerns generated by the presence of non-metallic inclusions.Especially the presence of aluminum oxide and spinel inclusions isconsidered as harmful both for the production process itself as for thesteel properties. These inclusions are mainly formed during thedeoxidation of the steel in the ladle, which is necessary for continuouscasting. Incomplete removal of the non-metallic inclusions duringsecondary metallurgy and reoxidation of the steel melt cause nozzleclogging during continuous casting. The layer of clogged materialcontains generally large clusters of aluminum oxide. Its thickness isrelated to the amount of steel cast as well as to the cleanliness of thesteel. Nozzle clogging results in a decreased productivity, because lesssteel can be cast per unit of time (as result of the decreasingdiameter) and due to replacement of nozzles with concurrent castinginterruptions. Besides clogging, the presence of reoxidation productsmay give rise to erosion of the nozzle and to the formation of inclusiondefects in the steel.

(2) Description of Related Art

Several solutions have been developed in the art to prevent steelreoxidation. In particular, the molten metal stream is generallyshrouded with a pouring shroud during its transfer from a casting vesselto a downstream vessel (or mold) to prevent direct contacts between thepoured steel and the surrounding atmosphere. Argon is often injecteddirectly at the surface of a pouring nozzle so as to shield the moltenmetal stream. The surface of the steel melt in a metallurgical vessel(for example a tundish) is generally covered with a liquid slag layer soas to prevent direct contacts between the steel and the surroundingatmosphere. Alternatively (or in addition), the atmosphere above thetundish can be made inert (by the use of an oxygen scavenger or of aninert gas such as argon).

Further solutions have been developed in the art to remove non-metallicinclusions and reoxidation products when they are present in thetundish. These solutions consist generally in facilitating the flotationof these inclusions and reoxidation products so that these are capturedby the floating slag layer. For example, dams, weirs, baffles and/orimpact pads can be used to deflect upwardly the molten metal stream inthe tundish. Inert gas bubbling devices can also be used to float outinclusions and reoxidation products.

Other solutions also exist for making the inclusions and oxidationproduct harmless. For example calcium based alloys can be used toeliminate some of the problems generated by the presence of aluminumoxide inclusions.

All these prior art solutions have contributed to improve the generalcleanliness of the steel. However, some of the prior art solutions can,in turn, generate new defects in the steel (as in gas bubbling, or theuse of a calcium-based alloy), can be expensive (as in the use of aninert atmosphere) or environmentally unacceptable. For these reasons, itwould be desirable to propose an alternative solution which would solvethe above problem, which would be economical and would not raiseenvironmental problems.

BRIEF SUMMARY OF THE INVENTION

The present invention is based on the hypothesis that, even though thesteel can be made relatively clean, it is impossible to keep it clean upto the mold in normal conditions. In particular, reoxidation of thesteel by chemical reaction between the refractory elements (generallymetal oxide) used in the continuous casting (vessel lining, slag,nozzles, stoppers, etc.) can also generate reoxidation products. Anotherpotential source of reoxidation is the oxygen permeating through theserefractory elements or through a permeable joint between the bottom walllining and the nozzle inlet or even the oxygen desorbed from therefractory element.

An object of the present invention is therefore to solve the aboveproblems by preventing the reoxidation products from reaching a castingnozzle and/or from forming in the immediate vicinity of or in thecasting nozzle.

According to the invention, this object is achieved by the use of asurrounding refractory element, an assembly of a nozzle and asurrounding refractory element, or an assembly of a nozzle and asurrounding refractory element housed in a tundish, in which the elementhas a base having a main surface, a bottom and a periphery surroundingthe main surface, in which the periphery has an exterior surface, andinterior surface and an upper face, and the intersection of the bottomof the base and the exterior surface of the periphery contains at leastone point at which the angle of intersection is not a right angle.

It is already known in the art to provide a surrounding element aroundthe pouring orifice of a tundish. FR-A-2394348 for example discloses aring intended to retain the steel in the tundish until a sufficientlevel and thereby a sufficient thermal mass is reached in order to avoidthe entry of “cold” steel into the pouring orifice. The prior arthowever fails to disclose an element with a base and a periphery, andthe intersection of the bottom of the base and the exterior surface ofthe periphery contains at least one point at which the angle ofintersection is not a right angle.

JP-A1-2003-205360 discloses a tundish for the continuous casting ofsteel. The well block of this tundish is comprised of two elements. Thenozzle is located inside the bottom part of the well block. Anadditional refractory element is positioned above the upper part of thenozzle to cover and protect the cement joint between the nozzle and thewell block. However, this document fails to disclose a refractoryelement with a base and a periphery, and the intersection of the bottomof the base and the exterior surface of the periphery contains at leastone point at which the angle of intersection is not a right angle.

WO2007/009667 discloses an element for use in conjunction with a nozzlein a metallurgical vessel. However, this document does not disclose arefractory element with a base and a periphery in which the intersectionof the bottom of the base and the exterior surface of the peripherycontains at least one point at which the angle of intersection is not aright angle.

Thanks to the particular arrangement according to the present invention,the reoxidation products and/or inclusions present in the metallurgicalvessel and which tend to accumulate on the bottom surface of the vesseland are carried down by the molten steel stream cannot reach the inletof the nozzle.

It must be understood that the element surrounding the nozzle can be ofany appropriate shape. In function of the metallurgical vessel design;it can be circular, oval or polygonal; its main orifice can be centralor eccentric. In an alternate embodiment of the invention, appropriateshapes for the element may exclude circular shapes. The elementsurrounding the nozzle can also be cut off so as to accommodate thosecases when one or more tundish walls are close to the pouring orifice.The main surface of the element can be planar or not (it can befrusto-conical, rippled, inclined). The nozzle can be an inner nozzle(for example in case the molten steel flow is controlled with a slidegate valve or if the installation is equipped with a tube or calibratednozzle changer) or a submerged entry nozzle or SEN (for example in thecase of stopper control). The metallurgical vessel or tundish can beequipped with one or more of such assemblies. The assembly can besupplied as a one-piece pre-assembled article (for example, co-pressed)or as separated articles.

As the element surrounding the nozzle need not be circular, and as theelement may be placed in a vessel that does not have circular symmetry,it may be important to align the element with the nozzle, and thereforewith the nozzle's surroundings, to produce desired flow patterns in thevicinity of the nozzle. Accordingly, the element and the nozzle may beconstructed with matching visual indicators or markings that, whenaligned or placed in contact, produce the desired geometricalarrangement of the element and the nozzle. Alternatively, the elementand the nozzle may be constructed with mating geometries so that, whenthese geometries are mated, the desired geometrical arrangement of theelement and nozzle, and of the combined element and nozzle with theirsurroundings, is produced. The mating geometries may be a matchingrecess and protrusion, a matching groove and lip, a matching peg andbore, a matching notch and protrusion, a matching dimple and mogul, amatching ridge and groove, aligned threaded receivers, aligned key orbayonet receivers, or matching non-circular surface geometries such asoval or polygonal faces. The mating geometry of the element may beplaced within its main orifice or on the bottom of the base. Theelement, considered alone, may contain, within its main orifice or onits base, one or more orienting geometries, such as pegs, bores,protrusion, recesses, notches, bevels, dimples, moguls, ridges, grooves,housings for screw or bayonet fittings, or shaped or threaded receiverportions. The bore of the element may be asymmetric, oval or polygonalin shape.

In certain embodiments of the invention, the element and the nozzle mayconstitute a single piece.

According to the present invention, the refractory element comprises abase having a main surface and a periphery surrounding the main surface;the upper face of the periphery being higher than the main surface ofthe refractory element. Thereby, a kind of deflecting trap is created inthe area surrounding the nozzle. It must be understood that the upperface of the periphery does not need to be planar. It can be waved orhave different heights along the periphery (for example higher in areaof the periphery close to a vessel lateral wall and lower on the otherside). The periphery may contain one or more interruptions or openings.The periphery may contain stepped changes in height, or may containgradual changes in height. The upper face of the periphery may have asawtooth configuration, a semicircular notch configuration, a squarenotch configuration, a wave configuration, a semicircular protrusionconfiguration or may contain one or more steps. The upper face of theperiphery may be in communication with an outwardly protruding lip. Theupper face of the periphery may be in communication with an inwardlyprotruding lip. The upper face of the periphery may be in communicationwith a plate or dome structure containing at least one port. Theperiphery may contain one or more ports; these ports may be circular,oval or polygonal in shape, and the ports may have horizontal axes, axesdirected upwards and inwardly, axes directed downwards and inwardly, oraxes that are not perpendicular to the external surface of theperiphery. The ports may be configured to have axes that are mutuallytangent to a circle within the periphery. Pairs of ports may beconfigured to have axes that intersect each other at a circle within theperiphery. The ports may be flared. In the inventive combination of atundish, a nozzle and a refractory element, the level of at least oneportion of the outer periphery of the refractory element is higher thanthe surface of the bottom wall of the tundish. Thereby, a secondobstacle is created around the nozzle tundish preventing the inclusionsor reoxidation products to reach its inlet. This type of arrangement isparticularly advantageous.

The periphery of the refractory element of the present invention maytake the form of a wall with measurements that are related to othermeasurements of the element by particular ratios or ranges of ratios. Incertain embodiments, the maximum height of the wall, measured from thebottom of the base, has a ratio of 1:1 to 6:1, or 1.1:1 to 6:1, to theminimum height of the wall, measured from the bottom of the base. Incertain embodiments, the maximum height of the wall, measured from thebottom of the base, has a ratio of 0.1:1 to 10:1, or 0.1:1 to 8.5:1, or0.2:1 to 8.5:1, or 0.5:1 to 8.5:1, to the maximum exterior diameter ofthe base. In certain embodiments, the wall has a minimum thickness of 2mm, 5 mm, or 10 mm. In certain embodiments, the wall has a maximumthickness of 60 mm, 80 mm, or 100 mm. In certain embodiments, the basehas a maximum thickness of 100 mm or 200 mm.

The periphery of the refractory element of the present invention maytake the form of a wall that has an exterior surface that has a portionthat is not vertical. In certain embodiments, the entire exteriorsurface of this wall is not vertical. In certain embodiments, the entirewall forms an obtuse angle with the main surface, as measured from theinterior of the element. In certain embodiments, the angle between thebottom surface of the base and the exterior surface of the wall has anangle lying within the ranges of 45 degrees to 89.5 degrees and 90.5degrees to 135 degrees. In certain embodiments, the angle between thebottom surface of the base and the exterior surface of the wall may varyaround the circumference of the element. In particular embodiments, theelement has non-vertical outer walls, and the element partially enclosesa volume with a cross-section that decreases in size with decreasingdistance to the nozzle or to a port in which the nozzle may be located.The walls may take the form of a cylinder with an axis that is notorthogonal to the horizontal plane. The walls may take the form of theradial surface of a truncated cone with a projected vertex below theplane of the main surface. The walls may take the form of the radialsurface of a truncated cone with a projected vertex above the plane ofthe main surface. The upper face of the periphery may form a circle,oval, or polygonal figure in a plane that is not parallel to the planeof the main surface.

The interior of the wall of the refractory element and the base of therefractory element may communicate, separately or together, with one ormore vanes. A vane may be disposed so that a projection of the plane ofthe vane intersects the axis of the nozzle. A vane may also be disposedso that no projection of a plane of the vane intersects the axis of thenozzle. The vanes may have surfaces and edges; the surfaces may beplanar, may be curved in one or two dimensions, and may be smooth orhave grooves. The edges of the vanes may be chamfered or have a sawtoothconfiguration, a semicircular notch configuration, a square notchconfiguration, a wave configuration, a semicircular protrusionconfiguration or may contain one or more steps.

The exterior of the wall of the refractory element may communicate withone or more vanes. A vane may be disposed so that a projection of theplane of the vane intersects the axis of the nozzle. A vane may also bedisposed so that no projection of a plane of the vane intersects theaxis of the nozzle. The vanes may have surfaces and edges; the surfacesmay be planar, may be curved in one or two dimensions, and may be smoothor have grooves. The edges of the vanes may be chamfered or have asawtooth configuration, a semicircular notch configuration, a squarenotch configuration, a wave configuration, a semicircular protrusionconfiguration or may contain one or more steps.

The surrounding refractory element may be made from a gas-imperviousmaterial. To be regarded as gas-impervious, such material has an openporosity (at the temperature of use) which is lower than 20% (thus lowerthan the open porosity of conventional lining material which istypically higher than 30%). For refractory materials, the permeabilityis generally related to the porosity. Therefore a low porosity materialhas a low permeability to gases. Such a low porosity can be obtained byincluding oxygen scavenger materials (e.g. antioxidants) in the materialconstituting the surrounding element. Suitable materials are boron orsilicon carbide, or metals (or alloys thereof) such as silicon oraluminum. In certain embodiments, they are used in an amount notexceeding 5 wt %. Alternatively (or in addition), products generatingmelting phase (for example B₂O₃) can also be included in the materialconstituting the surrounding element. In certain embodiments, they areused in an amount not exceeding 5 wt. %. Alternatively or (in addition),materials forming more voluminous new phases (either upon reaction orthe effect of the temperature) and closing thereby the existing porositycan also be included in the material constituting the preformed element.Suitable materials include compositions of alumina and magnesia.Thereby, steel re-oxidation in the area surrounding the nozzle isprevented. In certain embodiments of the invention, the refractorymaterial has a permeability value less than 15cD, 20cD, 25cD or 30cD,according to standard ASTM testing. A material that may be used contains0.5-1%, or 1-5% silica, 0.005% to 0.2% titania, 75% to 95% alumina, 0.1%to 0.5% iron (III) oxide, 0.5% to 1% magnesia, 0.1% to 0.5% sodiumoxide, 0.25% to 2% boron oxide, and 1% to 10% of zirconia+hafnia. Asuitable material may have a loss on ignition value of 0 to 5%.

The element, the nozzle or a layer of the element or the nozzle may bemade from a gas-impervious material. The nozzle or element may be madefrom refractory oxides (alumina, magnesia, calcia) and may beisostatically pressed. To be regarded as gas-impervious in the sense ofthe present invention, a 100 g sample of the candidate material isplaced in a furnace under argon atmosphere (a gentle stream of argon iscontinuously blown (about 11/min) into the furnace) and the temperatureis raised to 1000° C. The temperature is then raised progressively to1500° C. (in 1 hour) and is then left at 1500° C. for 2 hours. The lossof weight of the sample between 1000° C. and 1500° C. is then measured.This loss of weight must be lower than 2% for qualifying the material asgas-impervious. Thereby, not only the inclusion or reoxidation productscannot reach the nozzle but, in addition, they cannot form in the nozzleor the element. This particular combination provides thus a synergisticeffect according to which a perfectly inclusion- and reoxidationproduct-free steel can be cast.

The material constituting the nozzle or element can be selected fromthree different categories of materials:

a) materials which do not contain carbon;b) materials essentially constituted of non reducible refractory oxidesin combination with carbon; orc) materials comprising elements which will react with the generatedcarbon monoxide. Preferably, the selected material will present two orthree of the above categories.

Examples of suitable material of the first category are alumina,mullite, zirconia or magnesia based material (spinel).

Suitable materials of the second category are for example pure aluminacarbon compositions. In particular, these compositions should containvery low amounts of silica or of conventional impurities which areusually found in silica (sodium or potassium oxide). In particular, thesilica and its conventional impurities should be kept under 1.0 wt. %,preferably under 0.5 wt. %.

Suitable materials of the third category comprise for example free metalable to combine with carbon monoxide to form a metal oxide and freecarbon. Silicon and aluminum are suitable for this application. Thesematerials can also or alternatively comprise carbides or nitrides ableto react with oxygen compound (for example silicon or boron carbides).

In certain embodiments of the invention the selected material willbelong to the second or third categories; in certain embodiments of theinvention the selected material will belong to the second and thirdcategories.

A suitable material constituting the layer which will not produce carbonmonoxide at the temperature of use can comprise 60 to 88 wt. % ofalumina, 10 to 20 wt. % graphite and 2 to 10 wt. % of silicon carbide.Such a material contains oxygen getters such as non-oxide species suchas nitrides or carbides, or non-reducible oxides, which can react withany oxygen present.

In a variant, only a liner present at the steel contacting surface(inside and outside of the nozzle) is made from such a material. Inanother variant, the nozzle and the surrounding element are madeintegral (one-piece).

In case the joint between the surrounding element and the nozzle is notperfectly tight, it might be advantageous to provide a mortar jointwhich is made from a gas impervious mortar. Conventional mortars have anopen porosity of 30 to 50%. According to this advantageous embodiment,the mortar should have an open porosity of less than 20%. The mortar maybe made of a composition similar to, and processed in similar fashionto, the element or nozzle.

According to another of its aspects, the invention relates to aparticular surrounding refractory element which is used in the assemblyaccording to the invention. This surrounding element comprises a mainorifice adapted for matching engagement with at least a portion of theouter surface of the nozzle, a main surface surrounding the main orificeand an outer periphery surrounding the main surface, the level of theupper face of the periphery being higher than that of the main surface.Advantageously, the surrounding refractory element is made from agas-impervious material. Thereby, steel re-oxidation in the areasurrounding the nozzle is prevented. For example, a particularlysuitable composition to this end is essentially comprised of a highalumina material comprising at least 75 wt. % of Al₂O₃, less than 1.0wt. % of SiO₂, less than 5 wt. % of C, the reminder being constituted ofrefractory oxides or oxides compounds that cannot be reduced by aluminum(particularly aluminum dissolved in molten steel) at the temperature ofuse (for example calcia and/or spinel. A particularly suitable materialis the CRITERION 92SR castable available from VESUVIUS UK Ltd. Thismaterial is a high alumina low cement castable material reinforced withfused alumina-magnesia spinel. A typical analysis of this product is thefollowing:

Al₂O₃ 92.7 wt. % MgO 5.0 wt. % CaO 1.8 wt. % SiO₂ 0.1 wt. % Other 0.4wt. %

According to yet another of its aspects, the invention is directed to aprocess for the continuous casting of steel which comprises pouring themolten steel through an element, or a combination of a nozzle and anelement, as above described.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The invention will now be described with reference to the attacheddrawings in which

FIG. 1 shows a cross-section of the bottom wall of a metallurgicalvessel provided with an assembly according to the invention;

FIGS. 2 and 3 show respectively top and perspective views of asurrounding element according to the invention;

FIGS. 4 and 5 show skulls collected at the end of the casting operationsin the upper part of the nozzle;

FIG. 6 is a cross-section of an element according to the invention;

FIG. 7 is a cross-section of an element according to the invention;

FIG. 8 is a cross-section of an element according to the invention;

FIG. 9 is a perspective view of an element according to the invention;

FIG. 10 is a cross-section of an element according to the invention;

FIG. 11 is a cross-section of an element according to the invention;

FIG. 12 is a cross-section of an element according to the invention;

FIG. 13 is a perspective view of an element according to the invention;

FIG. 14 is a cross-section of an element according to the invention;

FIG. 15 is a perspective view of an element according to the invention;

FIG. 16 is a cross-section of an element according to the invention;

FIG. 17 is a cross-section of an element according to the invention;

FIG. 18 is a cross-section of an element according to the invention;

FIG. 19 is a cross-section of an element according to the invention;

FIG. 20 is a perspective view of an element according to the invention;

FIG. 21 is a perspective view of an element according to the invention;

FIG. 22 is a perspective view of an element according to the invention;

FIG. 23 is a perspective view of an element according to the invention;

FIG. 24 is a perspective view of an element according to the invention;

FIG. 25 is a perspective view of an element according to the invention;

FIG. 26 is a perspective view of an element according to the invention;

FIG. 27 is a perspective view of an element according to the invention;

FIG. 28 is a perspective view of an element according to the invention;

FIG. 29 is a perspective view of an element according to the invention;

FIG. 30 is a cross-section of an element according to the invention;

FIG. 31 is a cross-section of an element according to the invention;

FIG. 32 is a schematic perspective view of an element according to theinvention;

FIG. 33 is a schematic perspective view of an element according to theinvention;

FIG. 34 is a top view of an element according to the invention;

FIG. 35 is a top view of an element according to the invention;

FIG. 36 is a cross section of an element and a metallurgical vesselaccording to the invention;

FIG. 37 is an elevation of a portion of a raised outer periphery of anelement according to the invention;

FIG. 38 is an elevation of a portion of a raised outer periphery of anelement according to the invention;

FIG. 39 is an elevation of a portion of a raised outer periphery of anelement according to the invention;

FIG. 40 is an elevation of a portion of a raised outer periphery of anelement according to the invention;

FIG. 41 elevation of a portion of a raised outer periphery of an elementaccording to the invention; and

FIG. 42 is a perspective drawing of an element according to theinvention.

DETAILED DESCRIPTION OF THE INVENTION

The bottom wall 3 of a metallurgical vessel (here a tundish) isgenerally constituted of a permanent lining 33 made from refractorybricks or castable material. A working layer 32 of castable material isgenerally present above the permanent lining 33. The surface 31 of theworking layer will contact molten steel during the casting operations. Alayer of insulating material 34 is normally present under the permanentlining 33 in order to protect the metallic envelope 35 of themetallurgical vessel.

A nozzle 1 goes through the bottom of the tundish and serves to thetransfer of the molten steel from the tundish to the continuous castingmold. The nozzle is provided with an inlet 11 opening into a boredefining thus a passage 2 for the molten steel. The upper edge of theinlet is depicted as reference 12. FIG. 1 shows a submerged entry shroudor SES but, as explained above other kind of nozzles (such as an innernozzle) are also encompassed within the scope of the present invention.In the case of a SEN, the continuous casting operation is generallyprovided with a guillotine 37 to break the nozzle 1 and terminatecasting operations. Generally, the SEN is maintained in position by aramming mass 36.

The surrounding refractory element 4 surrounds the inlet portion 11 ofthe nozzle 1. The surrounding element 4 is comprised of a main surface41 surrounding a main orifice 40. The main surface has been representedfrusto-conical at FIG. 1 and planar at FIGS. 2 and 3, but, as explainedabove, other arrangements are possible. A raised outer peripherysurrounds the main surface 41; the raised outer periphery has aninterior face 105. The upper face 42 of the periphery is higher than thelevel of the main surface 41.

As can be seen on FIG. 1, it is advantageous to have the upper face 42of the periphery rising higher than the surface 31 of the tundish.

A mortar or cement joint at the junction 5 between the refractoryelement 4 and the nozzle 1 can be provided for further tightnessimprovement.

A trial has been performed to illustrate the effect of the invention.The solidified steel skull remaining in the inner nozzle at the end ofcasting operations has been collected and cut vertically in the middle.FIG. 4 (given by way of comparison) shows such a skull collected in aconventional installation (without the surrounding refractory element)and FIG. 5 shows such a skull collected in an installation according tothe invention.

The skull 20 of FIG. 4 shows significant disturbance in the region 21,21′ indicating the presence of alumina deposit on the inner wall of thenozzle. This alumina deposit is responsible for the clogging of thenozzle with all the detrimental consequences explained above. The skull20 of FIG. 4 shows also an enlarged portion in the region 22, 22′indicating a severe erosion of the nozzle inlet.

The skull 20 shown on FIG. 5 corresponds to the inner shape of thenozzle indicating thereby that the nozzle has neither been subjected toerosion nor to alumina clogging.

FIG. 6 shows a cross section of an element 4 of the present invention,in which base 102 contains main orifice 40 and base bottom face 104. Araised outer periphery is joined to the base; the raised outer peripheryhas an exterior face 106 and an upper face 42. Angles 108 are formedbetween element base bottom face 104 and exterior face 106 of the raisedouter periphery. In this embodiment, both of the angles shown in thecross-section representation are obtuse angles. In this embodiment, theheight of the raised outer periphery is constant.

FIG. 7 shows a cross section of an element 4 of the present invention,in which base 102 contains main orifice 40 and base bottom face 104. Araised outer periphery is joined to the base; the raised outer peripheryhas an exterior face 106 and an upper face 42. Angles 108 are formedbetween element base bottom face 104 and exterior face 106 of the raisedouter periphery. In this embodiment, both of the angles shown in thecross-section representation are obtuse angles. In this embodiment, theheight of the raised outer periphery varies around the course of theelement's circumference.

FIG. 8 shows a cross section of an element 4 of the present invention,in which base 102 contains main orifice 40 and base bottom face 104. Araised outer periphery is joined to the base; the raised outer peripheryhas an exterior face 106 and an upper face 42. Angles 108 are formedbetween element base bottom face 104 and exterior face 106 of the raisedouter periphery. In this embodiment, both of the angles shown in thecross-section representation are obtuse angles. In this embodiment,portions of the raised outer periphery with a fixed height are joined byheight transition segments 44.

FIG. 9 shows a perspective view of an element 4 of the present inventionhaving main orifice 40. A raised outer periphery is joined to the base;the raised outer periphery has an exterior face 106 and an upper face42. In this embodiment, all angles formed between the bottom face of thebase of the element and the exterior face of the raised outer peripheryof the element are obtuse. In this embodiment, the height of the raisedouter periphery varies around the course of the element's circumference.The plane of the upper face of the raised outer periphery and the planeof the bottom face of the base of the element are not parallel.

FIG. 10 shows a cross section of an element 4 of the present invention,in which base 102 contains main orifice 40 and base bottom face 104. Araised outer periphery is joined to the base; the raised outer peripheryhas an exterior face 106 and an upper face 42. Angles 108 are formedbetween element base bottom face 104 and exterior face 106 of the raisedouter periphery. In this embodiment, both of the angles shown in thecross-section representation are acute angles. In this embodiment, theheight of the raised outer periphery is constant.

FIG. 11 shows a cross section of an element 4 of the present invention,in which base 102 contains main orifice 40 and base bottom face 104. Araised outer periphery is joined to the base; the raised outer peripheryhas an exterior face 106 and an upper face 42. Angles 108 are formedbetween element base bottom face 104 and exterior face 106 of the raisedouter periphery. In this embodiment, both of the angles shown in thecross-section representation are acute angles. In this embodiment, theheight of the raised outer periphery varies around the course of theelement's circumference.

FIG. 12 shows a cross section of an element 4 of the present invention,in which base 102 contains main orifice 40 and base bottom face 104. Araised outer periphery is joined to the base; the raised outer peripheryhas an exterior face 106 and an upper face 42. Angles 108 are formedbetween element base bottom face 104 and exterior face 106 of the raisedouter periphery. In this embodiment, both of the angles shown in thecross-section representation are acute angles. In this embodiment,portions of the raised outer periphery with a fixed height are joined byheight transition segments 44.

FIG. 13 shows a perspective view of an element 4 of the presentinvention having main orifice 40. A raised outer periphery is joined tothe base; the raised outer periphery has an exterior face 106 and anupper face 42. In this embodiment, all angles formed between the bottomface of the base of the element and the exterior face of the raisedouter periphery of the element are acute. In this embodiment, the heightof the raised outer periphery varies around the course of the element'scircumference. The plane of the upper face of the raised outer peripheryand the plane of the bottom face of the base of the element are notparallel.

FIG. 14 shows a cross section of an element 4 of the present invention,in which base 102 contains main orifice 40 and base bottom face 104. Araised outer periphery is joined to the base; the raised outer peripheryhas an exterior face 106 and an upper face 42. Angles 108 are formedbetween element base bottom face 104 and exterior face 106 of the raisedouter periphery. In this embodiment, one of the angles shown in thecross-section representation is an acute angle; the other angle shown isan obtuse angle. In this embodiment, the height of the raised outerperiphery is constant around the course of the element's circumference.The plane of the upper face of the raised outer periphery and the planeof the bottom face of the base of the element are parallel.

FIG. 15 shows a perspective view of an element 4 of the presentinvention having main orifice 40. A raised outer periphery is joined tothe base; the raised outer periphery has an exterior face 106 and anupper face 42. In this embodiment, angles formed between the bottom faceof the base of the element and the exterior face of the raised outerperiphery of the element are acute, obtuse and, at two points, are rightangles. In this embodiment, the height of the raised outer peripheryvaries around the course of the element's circumference. The plane ofthe upper face of the raised outer periphery and the plane of the bottomface of the base of the element are not parallel.

FIG. 16 shows a cross section of an element 4 of the present invention,in which base 102 contains main orifice 40 and base bottom face 104. Araised outer periphery is joined to the base; the raised outer peripheryhas an exterior face 106 and an upper face 42. Angles 108 are formedbetween element base bottom face 104 and exterior face 106 of the raisedouter periphery. In this embodiment, one of the angles shown in thecross-section representation is an acute angle; the other angle shown isan obtuse angle. In this embodiment, the height of the raised outerperiphery varies around the course of the element's circumference. Theplane of the upper face of the raised outer periphery and the plane ofthe bottom face of the base of the element are not parallel.

FIG. 17 shows a cross section of an element 4 of the present invention,in which base 102 contains main orifice 40 and base bottom face 104. Araised outer periphery is joined to the base; the raised outer peripheryhas an exterior face 106 and an upper face 42. Angles 108 are formedbetween element base bottom face 104 and exterior face 106 of the raisedouter periphery. In this embodiment, one of the angles shown in thecross-section representation is an acute angle; the other angle shown isan obtuse angle. In this embodiment, the height of the raised outerperiphery varies around the course of the element's circumference. Theplane of the upper face of the raised outer periphery and the plane ofthe bottom face of the base of the element are not parallel.

FIG. 18 shows a cross section of an element 4 of the present invention,in which base 102 contains main orifice 40 and base bottom face 104. Araised outer periphery is joined to the base; the raised outer peripheryhas an exterior face 106 and an upper face 42. Angles 108 are formedbetween element base bottom face 104 and exterior face 106 of the raisedouter periphery. In this embodiment, one of the angles shown in thecross-section representation is an acute angle; the other angle shown isan obtuse angle. In this embodiment, the raised outer periphery has twoportions of constant height; these portions are joined by two heighttransition segments 44. The planes of the constant height portions ofthe upper face of the raised outer periphery and the plane of the bottomface of the base of the element are parallel.

FIG. 19 shows a cross section of an element 4 of the present invention,in which base 102 contains main orifice 40 and base bottom face 104. Araised outer periphery is joined to the base; the raised outer peripheryhas an exterior face 106 and an upper face 42. Angles 108 are formedbetween element base bottom face 104 and exterior face 106 of the raisedouter periphery. In this embodiment, one of the angles shown in thecross-section representation is an acute angle; the other angle shown isan obtuse angle. In this embodiment, the raised outer periphery has twoportions of constant height; these portions are joined by two heighttransition segments 44. The planes of the constant height portions ofthe upper face of the raised outer periphery and the plane of the bottomface of the base of the element are parallel.

FIG. 20 shows a perspective view of an element 4 of the presentinvention having main orifice 40. A raised outer periphery is joined tothe base; the raised outer periphery has an exterior face 106 and anupper face 42. In this embodiment, angles formed between the bottom faceof the base of the element and the exterior face of the raised outerperiphery of the element are obtuse. In this embodiment, the height ofthe raised outer periphery varies around the course of the element'scircumference. The plane of the upper face of the raised outer peripheryand the plane of the bottom face of the base of the element are notparallel. An element fin 120 protrudes from the interior face 105 of theraised outer periphery of the element. The fin surface nearest mainorifice 40 is at an angle from the vertical.

FIG. 21 shows a perspective view of an element 4 of the presentinvention having main orifice 40. A raised outer periphery is joined tothe base; the raised outer periphery has an exterior face 106 and anupper face 42. In this embodiment, angles formed between the bottom faceof the base of the element and the exterior face of the raised outerperiphery of the element are obtuse. In this embodiment, the height ofthe raised outer periphery varies around the course of the element'scircumference. The plane of the upper face of the raised outer peripheryand the plane of the bottom face of the base of the element are notparallel. Two element fins 120 protrude from the interior face 105 ofthe raised outer periphery of the element.

FIG. 22 shows a perspective view of an element 4 of the presentinvention having main orifice 40. A raised outer periphery is joined tothe base; the raised outer periphery has an exterior face 106 and anupper face 42. In this embodiment, angles formed between the bottom faceof the base of the element and the exterior face of the raised outerperiphery of the element are obtuse. In this embodiment, the height ofthe raised outer periphery varies around the course of the element'scircumference. The plane of the upper face of the raised outer peripheryand the plane of the bottom face of the base of the element are notparallel. Three element fins 120 protrude from the interior face 105 ofthe raised outer periphery of the element.

FIG. 23 shows a perspective view of an element 4 of the presentinvention having main orifice 40. A raised outer periphery is joined tothe base; the raised outer periphery has an exterior face 106 and anupper face 42. In this embodiment, angles formed between the bottom faceof the base of the element and the exterior face of the raised outerperiphery of the element are obtuse. In this embodiment, the height ofthe raised outer periphery varies around the course of the element'scircumference. The plane of the upper face of the raised outer peripheryand the plane of the bottom face of the base of the element are notparallel. An element fin 120 protrudes from the interior face 105 of theraised outer periphery of the element. The fin surface nearest mainorifice 40 is vertical.

FIG. 24 shows a perspective view of an element 4 of the presentinvention having main orifice 40. A raised outer periphery is joined tothe base; the raised outer periphery has an exterior face 106 and anupper face 42. In this embodiment, angles formed between the bottom faceof the base of the element and the exterior face of the raised outerperiphery of the element are obtuse. In this embodiment, the height ofthe raised outer periphery varies around the course of the element'scircumference. The plane of the upper face of the raised outer peripheryand the plane of the bottom face of the base of the element are notparallel. An element fin 120 protrudes from the interior face 105 of theraised outer periphery of the element. The fin extends upwardly abovethe maximum height of the upper face 42 of the raised outer periphery ofthe element.

FIG. 25 shows a perspective view of an element 4 of the presentinvention having main orifice 40. A raised outer periphery is joined tothe base; the raised outer periphery has an exterior face 106 and anupper face 42. In this embodiment, angles formed between the bottom faceof the base of the element and the exterior face of the raised outerperiphery of the element are obtuse. In this embodiment, the height ofthe raised outer periphery varies around the course of the element'scircumference. The plane of the upper face of the raised outer peripheryand the plane of the bottom face of the base of the element are notparallel. An element fin 120 protrudes inwardly from the interior face105 of the raised outer periphery of the element as well as outwardlyfrom the exterior face 106 of the raised outer periphery of the element.The fin extends upwardly above the maximum height of the upper face 42of the raised outer periphery of the element.

FIG. 26 shows a perspective view of an element 4 of the presentinvention having main orifice 40. A raised outer periphery is joined tothe base; the raised outer periphery has an exterior face 106 and anupper face 42. In this embodiment, angles formed between the bottom faceof the base of the element and the exterior face of the raised outerperiphery of the element are obtuse. In this embodiment, the height ofthe raised outer periphery varies around the course of the element'scircumference. The plane of the upper face of the raised outer peripheryand the plane of the bottom face of the base of the element are notparallel. An element fin 120 protrudes outwardly from the exterior face106 of the raised outer periphery of the element.

FIG. 27 shows a perspective view of an element 4 of the presentinvention having main orifice 40. A raised outer periphery is joined tothe base; the raised outer periphery has an exterior face 106 and anupper face 42. In this embodiment, angles formed between the bottom faceof the base of the element and the exterior face of the raised outerperiphery of the element are obtuse. In this embodiment, the height ofthe raised outer periphery varies around the course of the element'scircumference. The plane of the upper face of the raised outer peripheryand the plane of the bottom face of the base of the element are notparallel. An element fin 120 protrudes inwardly from the interior face105 of the raised outer periphery of the element. The fin extendsupwardly above the maximum height of the upper face 42 of the raisedouter periphery of the element.

FIG. 28 shows a perspective view of an element 4 of the presentinvention having main orifice 40. A raised outer periphery is joined tothe base; the raised outer periphery has an exterior face 106 and anupper face 42. In this embodiment, angles formed between the bottom faceof the base of the element and the exterior face of the raised outerperiphery of the element are obtuse. In this embodiment, the height ofthe raised outer periphery is constant around the course of theelement's circumference. The plane of the upper face of the raised outerperiphery and the plane of the bottom face of the base of the elementare parallel. A plurality of lateral ports 124 extends from interiorface 105 of raised outer periphery of the element to the exterior face106 of the raised outer periphery of the element. These ports may becylindrical, or may be flared at one end or at both ends.

FIG. 29 shows a perspective view of an element 4 of the presentinvention having main orifice 40. A raised outer periphery is joined tothe base; the raised outer periphery has an exterior face 106 and anupper face 42. In this embodiment, angles formed between the bottom faceof the base of the element and the exterior face of the raised outerperiphery of the element are obtuse. In this embodiment, the height ofthe raised outer periphery is constant around the course of theelement's circumference. The plane of the upper face of the raised outerperiphery and the plane of the bottom face of the base of the elementare parallel. A plurality of paired lateral ports 128 extends frominterior face 105 of raised outer periphery of the element to theexterior face 106 of the raised outer periphery of the element. Theseports may be cylindrical, or may be flared at one end or at both ends.These ports may be directed so that the longitudinal axes of each of apair of ports intersect at a circle within the volume partially enclosedby the element, i.e., the volume partially enclosed by the interior face105 of the raised outer periphery of the element.

FIG. 30 shows a cross section of an element 4 of the present invention,in which base 102 contains main orifice 40. A raised outer periphery 140is joined to the base; the raised outer periphery has an exterior face106. In this embodiment an externally directed rim 132 is incommunication with the exterior face 106 of the raised outer peripheryof the element. In the embodiment shown, externally directed rim 132 ishorizontal; it may be directed above or below the horizontal in otherembodiments.

FIG. 31 shows a cross section of an element 4 of the present invention,in which base 102 contains main orifice 40. A raised outer periphery 140is joined to the base; the raised outer periphery has an interior face105. In this embodiment an internally directed rim 134 is incommunication with the interior face 106 of the raised outer peripheryof the element. In the embodiment shown, the internally directed rimtakes a truncated conical form; it may be horizontal in otherembodiments.

FIG. 32 shows a schematic perspective view of an element 4 of thepresent invention, in which base 102 contains main orifice 40. A raisedouter periphery 140 is joined to the base. In the embodiment shown, theraised outer periphery has a gap.

FIG. 33 shows a schematic perspective view of an element 4 of thepresent invention, in which base 102 contains main orifice 40. A raisedouter periphery 140 is joined to the base. In the embodiment shown, theraised outer periphery has two gaps.

FIG. 34 shows a top view of an assembly of an element 4 of the presentinvention with a nozzle 1. The top view depicts the main surface 41 ofthe element and the outer periphery surrounding the main surface of theelement; the interior face 105 of the raised outer periphery is visible,as is the upper face 42 of the raised outer periphery. The interior ofthe main orifice 40 of the element has a non-circular geometryconfigured to mate with the exterior geometry of nozzle 1. In theembodiment shown, the respective geometries are hexagonal. Thecorresponding geometries constrain the positioning of the element 4about the nozzle, so that vertical and horizontal asymmetries of theelement can be properly positioned within a metallurgical vessel.

FIG. 35 shows a top view of an assembly of an element 4 of the presentinvention with a nozzle 1. The top view depicts the main surface 41 ofthe element and the outer periphery surrounding the main surface of theelement; the interior face 105 of the raised outer periphery is visible,as is the upper face 42 of the raised outer periphery. The interior ofthe main orifice 40 of the element has a non-circular geometryconfigured to mate with the exterior geometry of nozzle 1. In theembodiment shown, indentations on the interior of main orifice 40 acceptprotrusions on the surface of nozzle 1. The corresponding geometriesconstrain the positioning of the element 4 about the nozzle, so thatvertical and horizontal asymmetries of the element can be properlypositioned within a metallurgical vessel.

FIG. 36 shows a cross section of an element 4 and the walls 152 of ametallurgical vessel according to the invention. The nozzle and thefloor of the metallurgical vessel have been omitted for clarity. Astopper rod 154 is positioned to be moved vertically to permit orinterrupt flow through main orifice 40. The interior face 105 and theexterior face 106 of the raised outer periphery of the element areindicated. Gaps 162 between the element and the metallurgical vesselwall are indicated. The distance 164 between the interior face 105 andthe main orifice 40 is also indicated. The asymmetric design on theelement embodiment shown permits gaps of the same size between eachmetallurgical vessel wall 152 and the top of the element, as well aspermitting constant, or nearly constant, distances between the interiorface 105 and the main orifice 40, while allowing the stopper rod 154 tobe positioned closer to one metallurgical vessel wall than to the other.

FIG. 37 shows a portion 170 of the raised outer periphery of element 4.The upper face 42 of raised outer periphery of the element contains aplurality of square notches.

FIG. 38 shows a portion 170 of the raised outer periphery of element 4.The upper face 42 of raised outer periphery of the element contains aplurality of semicircular protrusions.

FIG. 39 shows a portion 170 of the raised outer periphery of element 4.The upper face 42 of raised outer periphery of the element is formed ina sawtooth pattern.

FIG. 40 shows a portion 170 of the raised outer periphery of element 4.The upper face 42 of raised outer periphery of the element contains aplurality of semicircular notches.

FIG. 41 shows a portion 170 of the raised outer periphery of element 4.The upper face 42 of raised outer periphery of the element is formed ina wave pattern.

FIG. 42 is a perspective drawing of an element 4 of the presentinvention, in which base 102 contains main orifice 40 and incommunication with raised outer periphery 140. Raised outer periphery140 houses upper face 42. The maximum external dimension of the base ofthe element 202, the minimum external dimension of the base of theelement 204, the maximum external dimension of the top of the element206, the minimum external dimension of the top of the element 208, thethickness of the base of the element 222, the thickness of the raisedouter periphery of the element 224, the maximum exterior height of theelement 232, the maximum interior height of the element 234, the minimumexterior height of the element 236, and the minimum interior height ofthe element 238 are indicated.

A refractory element according to the present invention, therefore, maycomprise a base having a bottom and a main surface, a main orificepassing through the main surface, and a periphery surrounding the mainsurface, wherein the main orifice has an interior face, wherein theperiphery has an interior face, an exterior face and an upper face,wherein the upper face of the periphery is higher than the main surfaceof the refractory element, wherein the periphery intersects the bottomof the base, and wherein the exterior face of the periphery forms anangle other than a right angle with the bottom of the base in at leastone point in their intersection. The exterior face of the periphery mayform a right angle with the bottom of the base at two points in theirintersection, may form an acute angle with the bottom of the base at allpoints in their intersection, or may form an obtuse angle with thebottom of the base at all points in their intersection. The plane of theexterior face of the periphery and the plane of the bottom of the basemay be non-parallel planes. The upper face of the periphery comprises anupper level and a lower level joined by two transitional non-vertical,non-horizontal portions. The main surface of the element may have ageometry selected from the group consisting of circular, oval, truncatedcircular, truncated oval, and polygonal geometry. The element may alsocomprise one or more fins extending from the inner face of theperiphery, or one or more fins extending from the exterior face of theperiphery. The element may comprise one or more ports passing from theexterior face to the interior face of the periphery. The element maycomprise a feature on its surface, for example on the interior face ofthe main orifice or on the bottom of the base, which may be a marking, arecess, a protrusion, a groove, a lip, a peg, a bore, a notch, a dimple,a mogul, a ridge, a threaded receiver, a key receiver, a bayonetreceiver, a bevel, and a non-circular geometry, or any other device orfeature which would constrain movement of the element around an axis.The refractory element of the invention may be composed of single piecesor of multiple pieces. The refractory element of the invention may beproduced from a high alumina material comprising at least 75 wt. % ofAl₂O₃, less than 1.0 wt. % of SiO₂, and less than 5 wt. % of C. Therefractory element may be constructed so that the periphery of theelement has a thickness equal to or less than 100 millimeters, and thebase of the element has a thickness equal to or less than 100millimeters.

An assembly of a refractory element and a nozzle according to theinvention may be composed of a single piece or multiple pieces. Therefractory element may comprise a main orifice having a non-circulargeometry, and wherein the refractory nozzle comprises an exterior radialsurface having a non-circular geometry configured to mate with therefractory element. The refractory element comprises a main orificeinterior face having a mating feature, wherein the refractory nozzlecomprises an exterior radial surface having a corresponding matingfeature configured to engage with the main orifice interior face matingfeature. The mating feature of the nozzle and the mating feature of theelement, when engaged, may prevent rotational motion of the elementaround the longitudinal axis of the bore of the nozzle.

An assembly of a refractory element and a nozzle according to thepresent invention may be deployed in a metallurgical vessel for thecasting of molten metal. In a typical deployment, the refractory nozzlemay have an inlet portion forming a passage through the bottom wall ofthe metallurgical vessel and a refractory element as previouslydescribed surrounding the inlet portion of the nozzle, wherein the inletportion of the nozzle has a top outer edge, wherein the inlet portion ofthe nozzle has a longitudinal axis, wherein the main orifice of theelement is adapted for matching engagement with at least a portion ofthe outer surface of the nozzle, wherein the main surface of the base ofthe element has a lowest level, the lowest level being lower than thetop outer edge of the nozzle inlet portion, and wherein at least aportion of the periphery of the refractory element is higher than thesurface of the bottom wall of the tundish. The element may comprise agas impervious refractory material. The nozzle or the element maycomprise a gas impervious refractory material. A gas impervious mortarmay be used between the nozzle and the refractory element.

A process for the continuous casting of steel may comprise pouring themolten steel from a ladle into a metallurgical vessel housing anassembly of a refractory element and a nozzle as described above, andthence into a casting mold.

Numerous modifications and variations of the present invention arepossible. It is, therefore, to be understood that within the scope ofthe following claims, the invention may be practiced otherwise than asspecifically described.

We claim:
 1. A refractory element for transferring molten metalcomprising: a base having a bottom and a main surface, a main orificepassing through the main surface, and a periphery surrounding the mainsurface, wherein the main orifice has an interior face and alongitudinal axis, wherein the periphery has an interior face, anexterior face and an upper face, wherein the upper face of the peripheryis higher than the main surface of the refractory element, wherein theperiphery intersects the bottom of the base, and wherein the exteriorface of the periphery forms an angle other than a right angle with thebottom of the base in at least one point in their intersection.
 2. Therefractory element of claim 1, wherein the exterior face of theperiphery forms a right angle with the bottom of the base at two pointsin their intersection.
 3. The refractory element of claim 1, wherein theexterior face of the periphery forms an acute angle with the bottom ofthe base at all points in their intersection.
 4. The refractory elementof claim 1, wherein the exterior face of the periphery forms an obtuseangle with the bottom of the base at all points in their intersection.5. The refractory element of claim 1, wherein the element partiallyencloses a volume with a cross-section that decreases in size withdecreasing distance to the bottom surface.
 6. The refractory element ofclaim 1, wherein the plane of the upper face of the periphery and theplane of the bottom of the base are not parallel.
 7. The refractoryelement of claim 1, wherein the upper face of the periphery comprises anupper level and a lower level joined by two transitional non-vertical,non-horizontal portions.
 8. The refractory element of claim 1, whereinthe main surface has a geometry selected from the group consisting ofcircular, oval, truncated circular, truncated oval, and polygonalgeometry.
 9. The refractory element of claim 1, further comprising avane extending from the interior face of the periphery.
 10. Therefractory element of claim 1, further comprising a plurality of vanesextending from the interior face of the periphery.
 11. The refractoryelement of claim 1, further comprising a vane extending from theexterior face of the periphery.
 12. The refractory element of claim 1,further comprising a plurality of vanes extending from the exterior faceof the periphery.
 13. The refractory element of claim 1, furthercomprising at least one port passing from the exterior face to theinterior face of the periphery.
 14. The refractory element of claim 1,further comprising a feature located at a position selected from thegroup consisting of the interior face of the main orifice and the bottomof the base, wherein the feature is selected from the list consisting ofa marking, a recess, a protrusion, a groove, a lip, a peg, a bore, anotch, a dimple, a mogul, a ridge, a threaded receiver, a key receiver,a bayonet receiver, a bevel, and a non-circular geometry.
 15. Anassembly for the transferring of molten metal comprising a refractoryelement according to claim 1, and a refractory nozzle in communicationwith the refractory element, wherein the nozzle has a bore having alongitudinal axis, and wherein the nozzle has an exterior radial surfaceconfigured to mate with the interior face of the main orifice.
 16. Theassembly of claim 15, wherein the axis of the nozzle bore is alignedwith the axis of the main orifice.
 17. The assembly of claim 15, whereinthe main surface of the base of the element has a lowest level, thelowest level being lower than the top outer edge of the nozzle inletportion.
 18. The assembly of claim 15, wherein the refractory elementand the refractory nozzle together comprise a single piece.
 19. Theassembly of claim 15, wherein the refractory element comprises a mainorifice having a non-circular geometry, and wherein the refractorynozzle comprises an exterior radial surface having a non-circulargeometry configured to mate with the refractory element.
 20. Theassembly of claim 15, wherein the refractory element comprises a mainorifice interior face having a mating feature, wherein the refractorynozzle comprises an exterior radial surface having a correspondingmating feature configured to engage with the main orifice interior facemating feature.
 21. The assembly of claim 20, wherein the mating featureand the corresponding mating feature, when engaged, prevent rotationalmotion of the element around the longitudinal axis of the bore of thenozzle.
 22. A metallurgical vessel for the casting of molten metalcomprising an assembly of a refractory nozzle having an inlet portionforming a passage through the bottom wall of the metallurgical vesseland a refractory element according to claim 1 surrounding the inletportion of the nozzle, wherein the inlet portion of the nozzle has a topouter edge, wherein the inlet portion of the nozzle has a longitudinalaxis, wherein the main orifice of the element is adapted for matchingengagement with at least a portion of the outer surface of the nozzle,wherein the main surface of the base of the element has a lowest level,the lowest level being lower than the top outer edge of the nozzle inletportion, and wherein at least a portion of the periphery of therefractory element is higher than the surface of the bottom wall of thetundish.
 23. The assembly of claim 15, wherein the element comprises agas impervious refractory material.
 24. The assembly of claim 15,wherein the nozzle comprises a gas impervious refractory material. 25.The assembly of claim 15, further comprising gas impervious mortarbetween the nozzle and the refractory element.
 26. The element of claim1, consisting essentially of a high alumina material comprising at least75 wt. % of Al₂O₃, and less than 1.0 wt. % of SiO₂, less than 5 wt. % ofC.
 27. Process for the continuous casting of steel comprising pouringthe molten steel from a ladle into a metallurgical vessel according toclaim 22, and from the metallurgical vessel into a casting mold
 28. Therefractory element of claim 1, wherein the periphery of the element hasa thickness equal to or greater than 2 millimeters, and equal to or lessthan 100 millimeters.